Creating Surface Flux Maps from Airborne Measurements: Application to the Mackenzie Area GEWEX Study MAGS 1999

Abstract

The objective of this study is to produce two-dimensional maps of the sensible and the latent heat fluxes from airborne measurements, based on the analysis of a flight pattern, called grid flights. A footprint model with along-wind and cross-wind components was used to project the measured fluxes onto the surface map. The method was applied to measurements over Arctic tundra during the Mackenzie Area GEWEX (Global Energy and Water Cycle Experiment) Study (MAGS) 1999. The resulting flux estimates were computed by integration of a wavelet transform, and corrected for long wavelength losses using information from 100 km long regional runs that were conducted close to the grid flights. The random flux error was estimated based on the flight length that is represented in each map element, and a map resolution of 3 × 3 km was chosen in order to keep the average random error of the latent heat flux below 25%. The random error of the sensible heat flux was smaller by a factor of 1.4 on average. An analysis of airborne flux measurements at different altitudes showed no significant increase of flux estimates for measurement heights below 90 m. Thus, the fluxes measured at heights between 48 and 64 m were not corrected for vertical flux divergence. The resulting flux maps provide quantitative two-dimensional estimates of the energy exchange between the surface and the atmosphere during the snow melt period in an Arctic environment, which are well-suited for calibration and validation of numerical models.

New calibration procedures for airborne turbulence measurements and accuracy of the methane fluxes during the AirMeth campaigns

“…Specifically, eddy covariance data from low-level flights can be used to create flux maps by means of direct surface projection (e.g. Mauder et al, 2008;Kohnert et al, 2017) and data fusion (e.g. Metzger et al, 2013;Serafimovich et al, 2018).…”

Flux measurements by the NRC Twin Otter atmospheric research aircraft: 1987–2011

“…The role of the NRC Twin Otter atmospheric research aircraft in MAGS was to provide measurements of surface-atmosphere exchange of sensible and latent heat and CO 2 at temporal and spatial scales suitable for model testing. Mauder et al (2008) used these data to demonstrate that flux measurements from a low-flying aircraft could be used to produce 2-dimensional maps of the sensible and latent heat flux for this complex ecosystem. Recent work has demonstrated how aircraft-based flux data can be used in combination with satellite-based input data to develop environmental response functions (Metzger et al, 2013).…”

Aircraft Regional-Scale Flux Measurements over Complex Landscapes of Mangroves, Desert, and Marine Ecosystems of Magdalena Bay, Mexico

“…Since the certification of the SDSU Sky Arrow, there have been numerous improvements and advancements in the electronics within the MFP (see, e.g., Hall et al 2006), including development of fast ultrasensitive temperature sensors (see, e.g., French et al 2001) not requiring the complex corrections described here, implementation of advanced integrated inertial measurement unit (IMU) and GPS (IMU-GPS) electronics (see, e.g., Garman et al 2006;Hall et al 2006;Vellinga et al 2010Vellinga et al , 2013, as well as more durable and robust BAT probes and pressure spheres (see, e.g., Eckman et al 2007;French et al 2004). New wind tunnel tests (Dobosy et al 2013;Garman et al 2006) and calibration techniques and procedures (Garman et al 2008(Garman et al , 2006Vellinga et al 2013) have improved the accuracy of wind vector calculations, while research into flux disaggregation methods Kirby et al 2008;Ogunjemiyo et al 2003) and surface flux mapping techniques (e.g., Mauder et al 2008) have improved associating surface fluxes to landscape elements in heterogeneous areas. Analysis strategies like the flightpath segmentation presented in Vellinga et al (2010) allow for regional-scale estimates of heterogeneous terrain from aircraft-based fluxes based on landscape characteristics.…”